"Expositions which are not intelligible to an educated man are scarcely worth the ink they are printed with. Whatever is clearly conceived can be clearly expressed." It is not surprising that the book _Force and Matter_ (1855)--in the preface to which these sentiments are expressed--went through sixteen editions in thirty years and was translated into most European languages. It is an extreme expression of the most thorough-going materialism, and the circumstance that its conclusions were acceptable neither to cautious scientists nor to critical philosophers, did not compromise its authority with the general public. As was only natural, for materialism is a creed for which the evidence is all on the surface, and to which the objections, being less obvious, escape notice. And Buechner's pleas for intelligibility and clearness, though in some sense justified by the inconceivable pedantry of much German metaphysics, was, in point of fact, only a form of cant; for "there are difficulties lying in the subject-matter itself which cannot be banished from the sphere of philosophy." Appeals to popular prejudices are not a more legitimate form of philosophic, than of scientific controversy; serious thinkers do not thus stoop to the expedients of the politician. EFFECTS OF DARWIN'S THEORY.--It would be a serious mistake, then, to imagine that materialistic naturalism had to wait for the publication of the _Origin of Species_ (1859) before it could become a formidable theory. And yet the appearance of Darwin's book had important effects, and among these is to be reckoned a certain weakening of the old "Argument from Design," according to which the complexity and delicacy evident everywhere in the world of nature, could not be attributed to chance, but pointed to the existence and activity of a divine Designer. Paley, during the eighteenth century, had elaborated the argument with a wealth of detailed instances of "contrivance": "The pivot upon which the head turns, the ligament within the socket of the hip-joint, the pulley or trochlear muscles of the eye; the epiglottis, the bandages which tie down the tendons of the wrist and instep," and so on.